1. Field of the Invention
The present invention relates to an image generating device and image generating method, and in particular, to an image generating device and image generating method whereby the relationship between moving objects moving within a virtual three-dimensional space and the surrounding environment, such as the path of travel, or the like, in a game device, or the like, can be represented more precisely and more realistically.
2. Description of the Related Art
With the progress of computer graphics technology in recent years, simulation devices and game devices have become widely used, in both industrial and domestic applications. One genre of game machines are devices portraying a car race game whereby a player competes by moving a car forming the object in the virtual game space, and such games are very popular.
Usually, game devices of this kind comprise a main unit containing an in-built computer device for executing previously determined game programs, an operating section for supplying operating signals indicating the movement of an object represented in the game to the device main unit, a monitor for displaying images accompanying the development of the game in accordance with the game program as executed by the main unit, and a sound device for generating sound accompanying the development of the game.
Since a car race game usually involves a game format where a player""s car competes against rival cars, then if a game is to be made to feel more realistic, it is of course necessary to achieve a more realistic simulation of the movement of the cars, and an important factor in this is the precision and realism of image processing depicting elements such as the relationship between the car and the roadway or terrain (environment) forming a portion of the background, and moreover, the relationship between the vehicle and the surrounding environment.
However, in the case of conventional game machines for playing car racing games, unresolved problems of the following kinds have arisen in seeking to represent, in the form of images, factors relating to interference between the vehicle and the surrounding environment occurring as the car travels on its path.
(1) In order to represent the travelling state of the vehicle as an image, it is necessary to determine impacts between the terrain and the tyres (wheels) of the vehicle at uniform time intervals. In recent years, terrain has been depicted by an appropriate number of polygon data, wherein the terrain is divided up very finely. Each element of polygon data contains positional co-ordinates for a plurality of vertices, and data for a single normal vector relating to the whole surface of the polygon. Since conventional impact judgement processing is carried out with respect to the actual surface of the polygons (polygon surface co-ordinates), then in cases where two polygons adjoin at a relatively large angle, the direction of impact judgement when the vehicle passes the joint between the polygons may change suddenly, causing the car to display unnatural behaviour. For example, even if the car is travelling along a section of road which appears to be relatively smooth, since there is a large angle between the polygon surfaces, the direction of the vehicle will change suddenly from a roll direction, to a pitch direction, to a yaw direction, hence creating an alien feel to the player.
Of course, if the size of a single polygon surface relating to the road surface or the terrain representing the surrounding environment is made extremely small compared to the size of the tyres, then the smoothness of the terrain as a whole will be improved accordingly and hence the aforementioned sudden changes in the direction of impact judgement will not be liable to occur. However, setting the polygon surfaces to a small size in this way entails a corresponding increase in the amount of data relating to the terrain, and hence the amount of storage capacity required in the memory becomes very large and the calculational load on the CPU of the computer device increases markedly. Even supposing that a memory with such a large storage capacity could be installed, there would still be a decline in processing speed in the device as a whole. Any decline in processing speed would be extremely disadvantageous in current game devices, and would have an effect on marketability. Consequently, there is a natural limit on the size to which the polygon surfaces can be set.
Furthermore, in addition to changes in behaviour between two polygon surfaces, the behaviour of the vehicle depicting fine indentations in each polygon surface is also extremely important in raising game realism. Conventionally, when seeking to depict this effect, height information for these indentations is previously stored for each polygon (texture), and it is necessary to judge impacts with respect to this indentation height information, creating a huge volume of data and computational load and hence proving impossible to achieve in practice.
Moreover, one of the factors where the behaviour of the vehicle affects the surrounding environment is the generation of dust clouds from the road surface and terrain accompanying the movement of the car. These dust clouds are an extremely important factor in creating a realistic depiction of the state of the road surface and the state of travel, namely, the speed and acceleration of the vehicle.
Despite this, conventionally, image processing relating to dust clouds has been very hard to achieve, and in many cases, dust clouds have not been depicted due to the poor quality of such depictions. Where an attempt has been made to represent dust clouds, this has simply involved superimposing one or a plurality of polygons representing the outer surface of a haze (cloud) of dust, three-dimensionally onto the background, or the like. Therefore, an object representing a cloud of dust having a very clearly defined outline is depicted flying out behind the car.
However, in reality, dust clouds are not often apparent at a single glance, and hence such representations have a very artificial appearance. Therefore, in order to create an impression of the particles making up the dust cloud, in many cases, an impression of dust particles has been introduced by means of image processing which reduces the presence of the cloud as a polygon, but even in these cases, the resulting dust clouds have lacked realism. Moreover, in some instances, for example, when a rival car accelerates past the player""s car, the position of the viewpoint camera may enter into the dust cloud atmosphere. In such cases, even though the viewpoint camera is located in the middle of a cloud of dust, conventionally, it has only been possible to generate an image of an unnatural state, where only the outer surface of the cloud of dust is visible, as if the camera is in a tunnel where only the walls of the tunnel are depicted.
A further factor whereby the moving vehicle interferes with the surrounding environment relates to the headlights and tail lamps lit up on the vehicle, and moreover, there is also light created by imaginary sunlight reflected by parts of the vehicle in the game space.
In a conventional game device, when such objects having high brightness are represented, a method is adopted whereby, either the colours of the objects themselves are depicted brightly, or they are depicted by using a fog effect created by an installed hardware unit, or they are depicted by placing a single layer, which changes from transparent to opaque from the edge of the light object towards the centre thereof, at the point of light emission and extending towards the player""s car.
However, these methods only depict light shining from the object, and none is capable of representing the orientation of the dispersed light from the moving object, which is an essential characteristic thereof, and hence the sensation of light emanating dynamically from the moving vehicle is lacking.
Looking at the example of headlights in the case of the third method described above, for instance, an unnatural effect is created whereby there is dispersion of light even when the vehicle in question is viewed from behind.
The present invention was devised in order to overcome the aforementioned unresolved problems associated with game devices, a common object thereof being to provide an image generating device and image generating method whereby factors relating to interference between a vehicle forming a moving body and the surrounding environment thereof, can be represented more realistically, hence increasing the sense of realism in games based on the main theme of a moving vehicle, and also raising the interest created thereby, without markedly increasing the computational load or data volume involved.
Specifically, a first object of the present invention is to provide an image generating device and image generating method having markedly improved realism and authenticity in the representation of vehicle behaviour compared to the prior art, by implementing more natural impact judgement processing which creates few alien effects by preventing sudden changes in the judgement direction in the case of impact judgement processing when a vehicle crosses the joint between two polygons, and by implementing impact judgement processing which takes indentations in the road surface into consideration, without markedly increasing the computational load or data volume involved therein.
It is a second object of the present invention to provide an image generating device and an image generating method whereby the alien effect created by conventional smooth or artificial-looking dust clouds is eliminated by depicting the sensation of particles making up a dust cloud, and furthermore, dust clouds can be represented without creating alien effects in the state of the cloud as viewed from the camera viewpoint, even in cases where the camera viewpoint is located spatially inside a dust cloud, without markedly increasing the computational load or data volume involved therein.
It is a third object of the present invention to provide an image generating device and image generating method whereby images of dispersed light having an orientation, such as headlights, tail lamps, or reflected light, emitted from a moving vehicle, can be generated in a dynamic fashion, and hence dispersed light can be represented in a more realistic manner, without markedly increasing the computational load or data volume involved therein.
In order to achieve the aforementioned objects, the image generating device relating to a first aspect of the invention comprises: impact establishing means for establishing the state of impact between an object and a path of travel specified by polygons in a virtual three-dimensional space; and generating means for generating image data representing a state where the object moves along the path of travel whilst maintaining the aforementioned state of impact; wherein the impact establishing means comprises: interpolating means for determining impact establishing data at an impact position of the object by interpolation from vertex data assigned to the vertices of the polygons of the path of travel; and impact specifying means for specifying the impact of the object on the path of travel in accordance with the impact establishing data interpolated by the interpolating means.
For example, the vertex data comprises the height and normal vector of each vertex, and the impact establishing data comprises the height and normal vector of the impact position. Moreover, for example, the interpolating means comprises: means for specifying respectively two edges of the polygon intersecting orthogonally and extending from the impact position in parallel with co-ordinate axes; means for setting a first and a second ridgeline on the basis of the vertex data for each end of the edges; means for determining respective data for the intersection points of the ridgelines with the two edges; means for specifying a third ridgeline of a segment having ends at the intersection points with the two edges; and means for determining the impact establishing data at the impact judging position from the respective data for the intersection points on this third ridgeline. Desirably, the first to third ridgelines are given as tertiary equations.
Moreover, the image generating device relating to a second aspect of the invention comprises: impact establishing means for establishing the state of impact between an object and a path of travel specified by polygons in a virtual three-dimensional space; and image data generating means for generating image data representing a state where the object moves along the path of travel whilst maintaining the aforementioned state of impact; wherein the impact establishing means comprises: correcting means for correcting the impact establishing data at the impact position of the object in accordance with the attributes of the path of travel represented by the polygons; and impact specifying means for specifying the impact of the object on the path of travel in accordance with the impact establishing data corrected by the correcting means.
For example, the impact establishing data is the height and normal vector of the impact position. Furthermore, for example, the attributes of the path of travel are indentations in the path of travel, and light and shade data supplied as texture for attaching to the polygons is used as information for the indentations.
The image generating device relating to a third aspect of the invention comprises: impact establishing means for establishing the state of impact between an object and a path of travel specified by polygons in a virtual three-dimensional space; and image data generating means for generating image data representing a state where the object moves along the path of travel whilst maintaining the aforementioned state of impact; wherein the impact establishing means comprises: interpolating means for determining impact establishing data at an impact position of the object by interpolation from vertex data assigned to the vertices of the polygons of the path of travel; correcting means for correcting the impact establishing data interpolated by the interpolating means in accordance with the attributes of the path of travel represented by the polygons; and specifying means for specifying the impact of the object on the path of travel in accordance with the impact establishing data corrected by the correcting means. For example, the impact establishing data is the height and normal vector of the impact position.
The image generating device relating to a fourth aspect of the invention comprises: dispersed light controlling means for controlling image data for dispersed light emitted from a light source on an object moving in a virtual three-dimensional space, in accordance with the state of movement of the object; and generating means for generating image data representing the state of movement of the object including this controlled image data for dispersed light.
Desirably, the dispersed light controlling means comprises: means for determining a light source vector representing the orientation of the light source and a line of sight vector representing the orientation of a camera viewpoint in the virtual three-dimensional space; means for specifying a single polygon as image data for the dispersed light; and changing means for changing the size of the polygon on the basis of information relating to the angle between the two vectors.
Moreover, desirably the changing means is means for changing the size of the polygon by multiplying by a coefficient which expands to infinity when the orientations of the two vectors coincide with each other.
The image generating device relating to a fifth aspect of the invention comprises: dust cloud controlling means for controlling image data for a dust cloud generated by an object moving in a virtual three-dimensional space, in accordance with the state of movement of the object; and generating means for generating image data representing the state of movement of the object including this controlled dust cloud image data.
In a desirable example of this case, the dust cloud controlling means comprises: means for specifying the dust cloud image data as a plurality of polygons; means for determining the degrees of physical influence exerted by factors including the behaviour of the object; means for calculating the respective behaviour of the plurality of polygons in accordance with these degrees of influence; and means for linking the plurality of polygons together and reconstituting same as a polygon group in accordance with these calculation results. Moreover, for example, the dust cloud controlling means may comprise means for applying processing to the reconstituted polygon group for imparting changes in transparency and a mist-like shape associated with the appearance of a dust cloud.
In any of the foregoing compositions, the object may be a car in a car race game moving in the virtual three-dimensional space.
The image generating method relating sixth aspect of the invention is an image generating method for generating image data representing the state of an object specified by polygons in a virtual three-dimensional space moving along a path of travel, whilst establishing the state of impact between the object and the path of travel, wherein impact establishing data at the impact position of the object is determined by interpolation from vertex data assigned to the vertices of the polygons of the path of travel, and the impact of the object on the path of travel is specified in accordance with this interpolated impact establishing data.
Moreover, the image generating method relating to a seventh aspect of the invention is an image generating method for generating image data representing the state of an object specified by polygons in a virtual three-dimensional space moving along a path of travel, whilst establishing the state of impact between the object and the path of travel, wherein impact establishing data at the impact position of the object is corrected in accordance with attributes of the path of travel represented by the polygons, and the impact of the object on the path of travel is specified in accordance with this corrected impact establishing data.
In the image generating method relating to an eighth aspect of the invention, the size and intensity of dispersed light emitted from a light source on an object moving in a virtual three-dimensional space are caused to increase as the direction of the dispersed light approaches the direction of a camera viewpoint in the space.
Moreover, in the image generating method relating to a ninth aspect of the invention, a dust cloud generated by an object moving in a virtual three-dimensional space is caused to change shape in accordance with the behaviour of the object, and the sense of transparency thereof is caused to increase towards the outer edges thereof.